Cellular Communications Flashcards
radio communication was invented by
Nikola Tesla and Guglielmo Marconi
He made the first public demonstration of wireless (radio) telegraphy
Nikola Tesla
He conducted long distance (over see) telegraphy in 1897
Guglielmo Marconi
first walkie-talkie was used by the US military
1940
from AT&T’s Bell Labs invented the transistor (semiconductor device used to amplify and switch electronic signals)
John Bardeen
Walter Brattain
William Shockley
1947
in 1979 the first commercial cellular phone service was launched by
Nordic Mobile Telephone (in Finland, Sweden, Norway, Denmark)
voice-oriented systems based on analog technology
1G (first generation)
Examples of 1G systems
Advanced Mobile Phone Systems (AMPS) and cordless systems
- voice-oriented systems based on digital technology
- more efficient and used less spectrum than 1G
2G (second generation)
Examples of 2G systems
Global System for Mobile (GSM)
US Time Division Multiple Access (US-TDMA)
high-speed voice-oriented systems integrated with data services
3G (third generation)
Examples of 3G systems
General Packet Radio Service (GPRS)
Code Division Multiple Access (CDMA)
still experimental, not deployed yet;
based on Internet protocol networks and will provide voice, data and multimedia service to subscribers
4G (fourth generation)
is a method used by service providers to improve the efficiency of a cellular network and to serve millions of subscribers using a limited radio spectrum
Frequency reuse
the entire network coverage area is divided into cells based on the principle of frequency reuse
Network Cells
basic geographical unit of a cellular network
cell
is the area around an antenna where a specific frequency range is used
cell
is represented graphically as a hexagonal shape, but in reality it is irregular in shape
cell
is a group of adiacent cells, usually 7 cells
cluster
their coverage is large (aprox. 6 miles in diameter); used in remote areas, high-power transmitters and receivers are used
macrocell
their coverage is small (half a mile in diameter) and are used in urban zones; low-powered transmitters and receivers are used to avoid interference with cells in another clusters
microcell
covers areas such as building or a tunnel
picocell
moving a call from one zone (from the transmitter-receiver from one zone) to another zone due to subscriber’s mobility
handover
allowing the subscriber to send/receive calls outside the service provider’s coverage area
roaming
when the subscriber enters another cell a unique frequency is assigned to him; used in analog systems
Frequency Division Multiple Access / FDMA
each subscriber is assigned a time slot to send/receive a data burst; is used in digital systems
Time Division Multiple Access / TDMA
each subscriber is assigned a code which is used to multiply the signal sent or received by the subscriber
Code Division Multiple Access / CDMA
this channel is used by a cellular phone to indicate its presence before a frequency/time slot/code is allocated to him
Control Channel
Cellular services (5):
◘ voice communication ◘ Short Messaging Service (SMS) ◘ Multimedia Messaging Service (MMS) ◘ Global Positioning System (GPS) ◘ Wireless Application Protocol (WAP) – to access the Internet
MSC
Mobile Switching Center
the coordinator of a cellular network, it is connected to several BSCs, it routes calls between BSCs; links the cellular network with other networks like PSTN through fiber optics, microwave or copper cable
Mobile Switching Center or MSC
BSC
Basic Station Controller
it is an interface between BTSs and it is linked to BTSs by cable or microwave links; it routes calls between BTSs; it is also connected to the MSC
Basic Station Controller or BSC
BTS
Base Transceiver Station
main component of a cell and it connects the subscribers to the cellular network
Base Transceiver Station or BTS
MSU
Mobile Subscriber Unit
Components of a cellular phone (6)
◘ radio transceiver ◘ antenna ◘ control circuitry ◘ man-machine interface ◘ subscriber identity module (SIM) ◘ battery (usually Li-ion)
formats the data sent to and from the BTS; controls signal transmission and reception
control circuitry
consists from a keypad and a display; is managed by the control circuitry
man-machine interface
integrated circuit card that stores the identity information of subscriber
SIM or subscriber identity module
GSM
Global System for Mobile Communication
global digital standard for cellular phones that offered roaming facility; used in Europe
Global System for Mobile Communication / GSM
first name of GSM before
Group Special Mobile
GSM operate in frequency bands of:
900MHz, 1800 MHz, 1900 MHz
IMEI
International Mobile Equipment Identity Key
a unique 15 digit number identifying each phone, is incorporated in the cellular phone by the manufacturer
International Mobile Equipment Identity Key / IMEI
is located on a white sticker/label under the battery, but it can also be displayed by typing *#06# on the phone
IMEI
IMSI
International Mobile Subscriber Identity Key
a 15-digit unique number provided by the service provider and incorporated in the SIM card which identifies the subscriber
International Mobile Subscriber Identity Key / IMSI
TMSI
Temporary Mobile Subscriber Identity Key
is a temporary number, shorter than the IMSI, assigned by the service provider to the phone on a temporary basis
Temporary Mobile Subscriber Identity Key / TMSI
Types of Registers: (3)
- HLR / Home Location Register
- VLR / Visitor Location Register
- EIR / Equipment Identity Register
is a database maintained by the service provider containing permanent data about each subscriber
Home Location Register (HLR)
database that stores temporary data about a subscriber; it is kept in the MSC of the of the area the subscriber is located in
Visitor Location Register (VLR)
database located near the MSC and containing information identifying cell phones
Equipment Identity Register (EIR)
- 1st level security mechanism for a GSM cellular network
- is a database that stores the list of authorized subscribers of a GSM network
Authentication Center (AuC)
is a switching center of the GSM network; coordinates BSCs linked to it
GSM Mobile Switching Center
GSM Uplink/BTS Transmit
935-960 MHz
1805-1880 MHz
1930-1990 MHz
GSM Downlink/BTS Receive
890-915 MHz
1710-1785 MHz
1850-1910 MHz
uplink and downlink channels have a bandwidth of
25 MHz
GSM carrier frequencies
124
GSM time slots for each carrier frequencies
0.577 ms
is used to communicate management data (setting up calls, location) between BTS and the cell phone within a GSM cell
GSM control channel
GSM control channels can have the following types: (3)
broadcast channel
common control channel
dedicated control channel
type of control channel used for the initial synchronization between the cell phone and the BTS
Broadcast Channel
Types of Broadcast Channel (3)
Frequency Correction Channel (FCCH)
Synchronization Channel (SCH)
Broadcast Control Channel (BCCH)
is composed from a sequence of 148 zeros transmitted by the BTS
Frequency Correction Channel / FCCH
follows the FCCH and contains BTS identification and location information
Synchronization Channel / SCH
contains the frequency allocation information used by cell phones to adjust their frequency to that of the network; is continuously broadcasted by the BTS
Broadcast Control Channel / BCCH
type of control chan. used for call initiation
Common Control Channels
the BTS uses this channel to inform the cell phone about an incoming cal
Paging Channel / PCH
is an uplink channel used by the cell phone to initiate a call
Random Access Channel / RACH
channel used to set up a call; once the cell phone has used PCH or RACH to receive or initiate a call, it uses __ to communicate to the BTS
Access Grant Channel / AGCH
control channel sed to manage calls
Dedicated Control Channels
used along with SACCH to send and receive messages; relays signalling information
Standalone Dedicated Control Channel / SDCCH
on the downlink BTS broadcasts messages of the beacon frequency of neighboring cells to the cell phones; on the uplink BTS receives acknowledgement messages from the cell phone
Slow Associated Control Channel / SACCH
used to transmit unscheduled urgent messages; is faster than SACCH as it can carry 50 messages per second, while SACCH an caryy only 4.
Fast Associated Control Channel / FACCH
GSM Security (3)
- Personal Identification Number (PIN)
- User Authentication
- TMSI-based Security
this security measure is within the cell phone and the service provider is not involved
Personal Identification Number / PIN